Vessels such as above ground liquid storage tanks require periodic cleaning to remove debris, sediment, algae and other contaminants that accumulate on the interior surfaces thereof, particularly on the bottom areas of the tank. Above ground liquid storage tanks, e.g. fuel tanks, may be as large as 5 feet in diameter by 8 feet long. Diesel fuel in particular has a tendency to encourage the growth of algae on the tank walls and floating in the stored fuel. Remediation of algae or other contaminants in the stored liquid requires periodic polishing, i.e. clarifying filtration, of the stored liquid. Polishing involves pumping the liquid out of the tank, through a filter and back into the tank, possibly running the process over a period of time until the liquid is free of particulate. Devices have been developed to efficiently clean tank interior walls without a person manually scrubbing the tank interior. For example, one tank cleaning device has multiple nozzles that rotate simultaneously around two mutually perpendicular axes and discharge pressurized streams of a liquid directed at the interior surface of the tank. The streams impinge on the interior tank surface to dislodge and wash away contaminants and general residue from the interior surface. This cleaning technique is commonly referred to as rotary impingement cleaning. Devices that perform rotary impingement cleaning are described in U.S. Pat. Nos. 6,123,271 and 6,561,199.
However, above ground storage tanks typically have small access ports, on the order of 2 inches in diameter. Known rotary impingement cleaning machines capable of thoroughly cleaning tanks as large as typical above ground storage tanks are generally too large to be inserted through a 2 inch opening. Therefore, a need exists for a device that can be inserted into a 2 inch opening that is capable of effectively cleaning the interior of above ground liquid storage tanks, especially including particulate residue on the tank bottom.